In such a rotary-piston pump, the piston rotor can for example be embodied as having multiple lobes, in particular two or three lobes, with the cross-section of the piston chamber viewed perpendicular to the axis of the rotary-piston pump being adapted to the eccentric trajectory of the piston rotor.
To achieve this, the piston rotor can, for example, be formed as trochoidal and the cross-section of the piston chamber or the shape of the surface that faces the piston rotor constitutes the corresponding envelope to this trochoid. Similarly, the cross-section of the piston chamber or the surface shape can describe a trochoid and the cross-section of the piston rotor constitutes the corresponding envelope.
In the present description of the invention, the term “central” refers to a position coaxial to or on the central axis of the piston chamber. The term “eccentric” is thus understood to be a position next to the central axis of the piston chamber.
Rotary-piston pumps of the above-mentioned design are generally known in the prior art, even in the blood supply field, for example in the form of an artificial heart. For example, DE 3317156 [U.S. Pat. No. 4,551,073] discloses a blood pump of this kind.
In a conventional embodiment, the rotary motion of the piston rotor in such a rotary-piston pump is transmitted with the aid of an eccentric. In this connection, according to the known prior art, the piston rotor is guided in its trajectory in the piston chamber with the aid of a gear transmission.
According to the known prior art, the mechanical components of the eccentric, in particular of the gear train, are medium-contacted, i.e. are in contact with the conveyed fluid such as blood or alternatively, seals are required to achieve a separation of the mechanical components from the conveyed fluid. Up to this point, however, the medium contact or the strict requirements with regard to tightness over time constitute as yet unsolved problems in such rotary-piston pumps.
Particularly when such rotary-piston pumps are used as blood pumps, the contact of the moving eccentric components of the prior art with the blood or a lack of tightness constituted significant problems since this can cause blood clots and can thus involve a risk of thrombosis. Blood deposits that are produced, for example despite seals that are used, can also result in a failure of the pump itself.